Thread: S-38B Question
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Old March 11th 12, 07:35 AM posted to rec.radio.amateur.boatanchors
coffelt2 coffelt2 is offline
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First recorded activity by RadioBanter: Jul 2009
Posts: 70
Default S-38B Question

Yikes! That's why you could get quite a jolt just from the cabinet, and it
wasn't too cool
to use the S-38 right next to a grounded piece of gear. I think I remember
something in
QST "Hints and Kinks" about putting a light bulb (small wattage) between the
S-38's cabinet
and an adjacent, grounded piece of gear. If the lamp illuminated, reverse
the S-38's AC
wall plug.

Old Chief Lynn, W7LTQ


"DaveW" wrote in message
...
I checked the schematic notes and the inverted pyramid symbol is the
chassis ground. The other symbol is the cabinet ground. Apparently the
chassis is isolated from the cabinet except for a single 0.25 mfd capacitor
which connects the two.

DaveW


"coffelt2" wrote in message
...
First, I don't have an answer, but am preparing to recap an even older
S-38 myself. I think I remember
from many, many years ago, that some of those "hot chassis" rigs had two
ground systems, that were actually connected together at some point.
Something about "ground loops" and hum
reduction. In the schematic you linked here, there are two different
ground symbols. Could one be the actual chassis connection, and the other
sort of a slightly "lifted" or signal/RF ground? Just guessing, hope
someone knows the real answer!

Old Chief Lynn, W7LTQ


"DaveW" wrote in message
...
I've begun the restoration of an S-38B. Just started to replace the
filters an I already have a question. The old multi-section cap ground
is connected to pin 2 of the 35Z5 rather than directly to the chassis
ground as shown in the schematic he
http://i1206.photobucket.com/albums/...gFilterCap.png
Pin2 is connected to the chassis ground through the filament string,
which has a 125 ohm resistance when cold. Is this a problem or were all
S38's wired in this manner?

The filter cap appears to be original but you can't always be certain.
It's clear other repairs have been made during its lifetime.

If anyone can recall recapping an S-38 I'd be interested in your
observation regarding the filter cap ground wire location.

Thanks,

DaveW